1. Field of the Invention
The present invention relates to a gas turbine moving blade provided with a turbulator, and more particularly to an arrangement of a turbulator of a leading edge cooling passage within a gas turbine moving blade.
2. Description of the Related Art
FIG. 4 is a cross-sectional view showing a normal conventional moving blade. In FIG. 4, a moving blade having a leading edge 17 and a trailing edge 16 as a whole is generally designated by reference numeral 11. A cooling passage 17 is provided inside of the leading edge 12. Reference numerals 13, 14 and 15 denote cooling passages which are in communication with each other to form a serpentine cooling passage. Cooling air 20 passes through a cooling passage 12 on the leading edge 17 side and cools the leading edge portion to flow out of a tip end portion of the moving blade 11. Cooling air 21 is introduced into the cooling passage 13 to flow toward a tip end portion 21a where the cooling air flows to the next cooling passage 14. Then, the cooling air 21 flows toward a proximal end portion of the cooling passage 14 and flows toward the cooling passage 15 on the side of the trailing edge 16 through a proximal end portion 21b to be discharged from a combustion gas passage 21c through a number of air holes provided in the trailing edge 16.
FIG. 5 is an enlarged cross-sectional view taken along the line C--C of FIG. 4. A number of turbulators 28 are provided in a multi-stage manner from top to bottom of both wall surfaces within the cooling passage 12 on the side of the leading edge 17. The turbulators 28 are provided to make the stream of the introduced cooling air 20 turbulent to enhance heat transmission.
FIG. 6 is an enlarged longitudinal sectional view of a part of the cooling passage 12 on the side of the leading edge 17. A rib 31 is provided in the interior on the side of the leading edge 17 of the moving blade 11 whereby the cooling passage 13 and the cooling passage 12 are partitioned from each other to define the cooling passage 12. The plurality of turbulators 28 which are slanted upwardly in the direction of combustion gas flow G over the upper and lower portions of both wall surfaces of this cooling passage 12, i.e., which are slanted in the direction of gas flow the cooling air 20 toward the downstream side of the direction of combustion gas flow G are arranged on both wall surfaces of the cooling passage 12. The cooling air 20 is introduced from the proximal end portion of the moving blade 11 to flow toward the tip end thereof to cool the interior of the leading edge 17 from the inside. However, the cooling air that flows upwardly along both wall surfaces of the cooling passage 12 is caused to impinge against the turbulators 28. By this impingement, as shown in the drawing, secondary flows 20b along the slant of the turbulators 28 toward the rib 31 are generated at each turbulator 28. As a result, high heat transmission efficiency is obtained at the rib 31 (portion D indicated by the broken line) at a border between each turbulator 28 and the adjacent cooling passage 13 with which each turbulator 28 continue.
However, it is impossible to obtain this cooling effect at the portion D on the rib 31 side at the side of the leading edge 17 (portion E indicated by the broken line) with which each turbulator 28 is continuous. The heat transmission on the leading edge side which is most frequently exposed to the high temperature combustion gas is lowered. Although the turbulators 28 are attached to the cooling passage 12 so that the heat transmission efficiency may be enhanced as a whole, as shown in FIG. 6 and as described above, it is impossible to obtain a satisfactory effect for cooling the leading edge 17 which most needs the cooling effect, i.e., for cooling the portion E. Accordingly, it is desired to enhance the heat transmission efficiency in this portion.
Also, if the turbulators are provided, the heat transmission efficiency is enhanced but on the other hand, the pressure loss of the cooling air is increased. Accordingly, it is necessary to improve the mutually inconsistent phenomenon of enhancement of the heat transmission and the loss of the pressure. In view of these two factors, it is necessary to optimize the arrangement of the turbulators.